Several clerics have issued fatwas against former Pakistani Minister Sherry Rehman and declared her an infidel for calling for changes in the blasphemy law.

According to a report by Xavier Patras William, the acting CEO of human rights organisation "Life for All", that has prompted activists to file a complaint with police in the port city of Karachi.

Media reports said the imam of Sultan Masjid, one of Karachi's biggest mosques, declared Rehman a "kaafir" (infidel) and "wajib-ul-qatl" (fit to be killed) while delivering a sermon after Friday prayers.

William said the mosque has close ties to the Saudi Arabian government.

According to William, Islamic hardliners who organised a massive rally in Karachi also published material calling Rehman a person who "has invoked the religious honour of Pakistan's Muslims" after calling for changes in the blasphemy law.

The threats came days after a police guard gunned down Punjab Governor Salmaan Taseer for criticising the blasphemy law.

William said activists have filed a complaint against the imam of Sultan Masjid at the Darakhsan police station in Karachi.

The complaint was registered on behalf of Rehman, a senior leader of the Pakistan People's Party (PPP), Salmaan Taseer's son Shaan Taseer and journalist Ali Chishti.

In the complaint, William said, the activists alleged that the imam of Sultan Masjid had also praised Mumtaz Qadri, the policeman who assassinated Taseer.

Chishti told the media that activists feared for Rehman's life following the murder of the Punjab Governor.

According to William, the activists said they were proud to be Muslims but rejected murdering people in the name of Islam.

William said hardliners have been gunning for Rehman since she tabled a private bill in parliament to remove the mandatory death sentence for blasphemy.

Reports have said Rehman has been facing pressure from within the PPP to leave Pakistan for her own security.

According to William, security has been enhanced at Rehman's residence in Karachi and she has told the media she will not leave Pakistan.